Most electrified trains utilise pantographs to transmit electricity from an overhead wire to the train. Pantographs of modern high speed, electrified trains comprise carbon current collectors. These carbon current collectors typically comprise a carbon block support and a carbon block that contacts the wire. The carbon block functions inter alia to minimise the wear on the overhead wire. A major problem with the carbon blocks is that they are susceptible to crack damage. Misalignment of electrical sectioning equipment, excessive arcing and constant friction can all cause significant damage to the carbon block. If not detected and repaired, such damage can cause dewirement and/or damage to the pantograph generally and therefore render a train inoperable. To detect damage to pantographs it is common practice for the operators of railways to conduct manual inspections at regular intervals. This process requires relocation of the train to be inspected to a service depot, electrical isolation of the overhead wires and access to the top of the train. The labour costs and operational down time associated with such an inspection process are clearly undesirable. A number of systems have been developed to circumvent the manual gauging of pantographs. GB1374972 and GB2107662 describe systems that measure pantograph damage in which tubes are placed within a cavity of a pantograph current collector. If sufficient damage is sustained by the pantograph, the tube ruptures causing a drop in system pressure. This loss is detected and the system automatically lowers the pantograph, thereby preventing further damage to the pantograph and/or the overhead wire. EP-A-0269307, DE-U-8803377.5 and EP-A-0525595 describe systems in which optical fibres are embedded near the wear surface of a pantograph current collector. Optical signals are transmitted in the fibres and if damage to a fibre results, the loss of the optical signal in that fibre indicates pantograph damage and/or wear. Another approach described in Engineering Integrity, Volume 19, March 2006, pp. 12-17 employs a laser assisted image processing technology to automatically detect pantograph carbon current collector wear.
While the systems described above are effective at monitoring pantograph damage and/or wear they suffer from the disadvantage that they are cost prohibitive. The system described in Engineering Integrity, Volume 19, March 2006, pp. 12-17 suffers from the added disadvantage that locomotives must be relocated to a designated monitoring station and therefore taken out of normal service. Moreover, the system can only guarantee accuracy of measurement if the locomotive is traveling less than 12 kilometers per hour (kph) at the monitoring station.
It is an aim of the invention to provide a cost-effective system that automatically monitors the condition of a pantograph, while a locomotive comprising the pantograph is in normal service. The invention aims further to overcome or ameliorate one or more of the disadvantages or problems described above, or at least provide the consumer with a useful choice.